1. Technical Field
The present disclosure relates to particleboard and methods for fabricating particleboard (e.g., from natural fibers/materials, such as coconut-based materials) and, more particularly, to particleboard (e.g., formaldehyde-free particleboard) utilizing natural fibers/materials (e.g., lignocellulosic materials), wherein the particleboard has improved performance characteristics and/or mechanical properties.
2. Background Art
In general, particleboard is an engineered panel product manufactured from wood particles (e.g. wood chips, sawmill shavings and/or sawdust) and/or other lignocellulosic particles and fibers (e.g. hemp, kenaf, jute and/or cereal straw), which are typically pressed and bonded together using a binder (see, e.g., Wallenberger et al., Natural fibers, plastics and composites, Chapter 14: Uses Of Natural Fiber Reinforced Plastics, Kluwer Academic Pub. (2004) 249-53). It is noted that while some in the industry may generally differentiate some classes of bonded boards such as, for example, particleboard, fiber-board and others, the term particleboard is used in the present disclosure to include the products (e.g., particleboard, bonded-board, fiber-board, etc.) that may be fabricated utilizing the systems and methods of the present disclosure, as described below.
Particleboard is often used for indoor products including cupboards, built-in furniture, and shelving, as well as for many other construction applications or the like. In general, urea-formaldehyde (UF) and phenol-formaldehyde (PF) resins are typical binders used by the particleboard industry due to a variety of reasons (e.g., low cost, ease of use, a variety of curing conditions, low cure temperature, short curing time, water solubility, resistance to microorganisms and to abrasion, thermal properties, strength and water resistance) (see, e.g., El-Wakil et al., Modified Wheat Gluten As A Binder In Particleboard Made From Reed, Journal of Applied Polymer Science, (2007) 106(6), 3592-99; and Maloney, T. M., The Family Of Wood Composite Materials, Forest Products Journal (1996) 46(2), 19-26).
However, UF and PF resins are generally neither eco-friendly nor safe due to health effects of exposure to formaldehyde emissions (see, e.g., Marutzky, R., Release Of Formaldehyde By Wood Products, Wood Adhesives—Chemistry And Technology, Marcel Dekker, Inc., (1989) 307-87; Henderson, J. T., Volatile Emissions From The Curing Of Phenolic Resins, TAPPI Journal (1979) 62(8), 93-96; Meyer et al., Formaldehyde Release From Wood Products: An Overview, ACS symposium series 316: Formaldehyde Release From Wood Products, (1986), 1-16; Groah, W. J., Formaldehyde Emissions: Hardwood Plywood And Certain Wood Based Panel Products, ACS symposium series 316: Formaldehyde release from wood products, (1986) 12-26; Baumann, M. G. D., Aldehyde Emission From Particleboard And Medium Density Fiberboard Products, Forest Products Journal, (2000) 50(9), 75-82; Mo, X. et al., Compression And Tensile Strength Of Low Density Straw-Protein Particleboard, Ind. Crops Prod. (2001) 14, 1-9).
Moreover, formaldehyde-based adhesives are derived from generally unsustainable petrochemicals. Therefore, formaldehyde-free adhesives from renewable resources have been developed for the wood composites industry. In general, natural adhesives based on proteins such as soy protein, wheat gluten, and milk casein are an attractive alternative for an environmentally friendly binder for particleboard production (see, e.g., Lei, H. et al., Gluten Protein Adhesives For Wood Panels, J. of Adhesion Science and Tech. (2010), 24, 1583-1596; Nordqvist et al., Comparing Bond Strength And Water Resistance Of Alkali-Modified Soy Protein Isolate And Wheat Gluten Adhesives, Int'l J. of Adhesion & Adhesives (2010) 30, 72-79; Khosravi et al., Protein-Based Adhesives For Particleboards, Industrial Crops and Products (2010) 32, 275-83; Sun et al., Bio-Based Polymers And Composites, Elsevier Inc., (2005) 292-368; Hettiarachchy et al., Alkali-Modified Soy Protein With Improved Adhesive And Hydrophobic Properties, J. Am. Oil Chem. Soc. (1995) 72, 1461-64; Wang et al., Low Density Particleboard From Wheat Straw And Corn Pith, Ind. Crops Prod. (2002) 15, 43-50; Zhong et al., Wet Strength And Water Resistance Of Modified Soy Protein Adhesives And Effects Of Drying Treatment, J. Polym. Environ. (2003) 11, 137-44; Leiva et al., Medium-Density Particleboards From Rice Husks And Soybean Protein Concentrate, J. Appl. Polym. Sci. (2007) 106, 1301-06).
In general, wheat gluten (WG) is a complex protein derived from wheat, and has been investigated for potential use in food and non-food applications. In the last decades, environmental concerns about an increase in non-degradable plastic waste have generated interest in biopolymers from renewable natural sources. WG-based plastics can potentially be used to substitute conventional petroleum-based plastics due to their non-toxicity, large-scale availability, low cost, biodegradability, and environmentally friendly properties (see, e.g., Bietz et al., Properties And Non-Food Potential Of Gluten, Cereal Foods World (1996) 41, 376-82).
However, some of the plastics made from WG are brittle, and generally absorb water after being processed. Some approaches to improve the mechanical properties and water resistance of WG have been developed. For example, the addition of additives such as synthetic and natural fibers to reinforce WG is one approach to tailor the mechanical properties of WG plastics. Some advantages of natural fibers over traditional reinforcing and man-made fibers (e.g. glass, carbon, aluminum oxide and Kevlar) are their low cost, low density, good specific mechanical properties, high toughness, non-abrasive behavior during processing, enhanced energy recovery, and biodegradability (see, e.g., Avella et al., Eco-Challenges of Bio-Based Polymer Composites, Materials (2009) 2, 911-25).
In general, these advantages make the natural fibers a potential replacement for the conventional reinforcement materials in composites. However, some of the potential drawbacks of the natural fibers in the composites are incompatibility with many hydrophobic polymer matrices, and relatively high moisture absorption (see, e.g., Saheb et al., Natural Fiber Polymer Composites: A Review, Advances in Polymer Tech. (1999) 18(4), 351-63). Therefore, some chemical surface treatments have been considered to modify the fiber surface properties, typically resulting in improved fiber-matrix adhesion. Some of these chemical treatments include de-waxing, alkali treatment, peroxide treatment, acetylation, acrylation, benzoylation, treatment with various coupling agents, and others (see, e.g., Mohanty et al., Surface Modifications Of Natural Fibers And Performance Of The Resulting Biocomposites: An Overview, Composite Interfaces (2001) 8(5), 313-43).
In general, the thiol groups (—SH) of cysteine in the WG protein play a role in adhesion. At a high temperature, a thiol/disulfide interchange reaction typically occurs, thus cross-linking the protein to form a three dimensional network (see, e.g., Schofield et al., The Effect Of Heat On Wheat Gluten And The Involvement Of Sulphydryl-Disulphide Interchange Reactions, J. Cereal Sci. (1983) 1, 241-53; Fernandes et al., Theoretical Insights Into The Mechanism For Thiol/Disulfide Exchange, Chem. Eur. J. (2004) 10, 257-66; Pommet et al., Study Of Wheat Gluten Plasticization With Fatty Acids, Polymer (2003) 44, 115-22).
Thus, during particleboard preparation by hot-press molding, the cross-linking reaction of WG typically occurs. In general, during hot-press molding, some phenolic hydroxyl groups of lignin in wood particles or lignocellulosic materials are oxidized to form quinines. The thiol groups in WG can then react with the quinines through the Michael addition reaction, typically resulting in adhesion between wood particles or lignocellulosic materials and the WG adhesives (see, e.g., Takasaki et al., Formation Of Protein-Bound 3,4-Dihydroxyphenylalanine And 5-S-Cysteinyl-3,4-Dihy-Droxyphenylalanine As New Cross-Linkers In Gluten, J. Agric. Food Chem. (1997) 45, 3472).
In general, coconut fiber and coconut coir pith (coco peat) are derived from coconut husks. Coconut fiber (CCF) is lignocellulosic fiber typically extracted from the husk of coconut fruit obtained from coconut palm trees (Cocos nucifera), which are abundantly available in tropical countries. The coconut pith is the particulate generally obtained after long fibers are removed from the coconut husk. Coconut fiber can be used to make, for example, rope, yarn, floor mats, mattresses and brushes, while the pith material is typically manufactured into industrial adsorbents, composting material or plant growing systems. However, a small percentage of the coconut fiber and coconut pith is consumed for conventional uses, and much of it still remains unused.
In general, CCF possesses many advantages. For example, it is inexpensive, moth-proof, generally resistant to fungi and rot, not easily combustible, flame-retardant, it provides excellent insulation against temperature and sound, and it is amenable to chemical modification. Moreover, CCF is tough and durable. In general, it is the most ductile fiber amongst the natural fibers, capable of taking about 4-6 times more elongation than other fibers (see, e.g., Ali, M., Coconut Fibre—A Versatile Material And Its Applications In Engineering, Second Int'l Conference on Sustainable Construction Materials and Tech. (2010) Main Vol. 3, Paper 13, 1441-54).
CCF has been used as reinforcement in order to modify the properties of many polymers, such as polyester, polyester amide, polyacrylate, polypropylene, linear low density polyethylene (LLDPE), high impact polystyrene (HIPS), polyurethane, poly-3-hydroxy butyrate co-valerate (PHBV), starch/ethylene vinyl alcohol copolymers blend, and natural rubber.
5. See, e.g., Rout et al., The Influence Of Fiber Surface Modification On The Mechanical Properties Of Coir-Polyester Composites, Polymer Composites (2001) 22(4), 468-76; Rout et al., The Influence Of Fibre Treatment On The Performance Of Coir-Polyester Composites, Composites Science and Tech. (2001) 61 1303-10; Hill et al., Effect Of Fiber Treatments On Mechanical Properties Of Coir Or Oil Palm Fiber Reinforced Polyester Composites, J. of Applied Polymer Science (2000) 78(9), 1685-97; Hill et al., The Effect Of Environmental Exposure Upon The Mechanical Properties Of Coir Or Oil Palm Fiber Reinforced Composites, J. of Applied Polymer Science (2000) 77(6), 1322-30; Varma et al., Coir Fibers, J. of Reinforced Plastics and Composites (1985) 4(4), 419-29; Abdul Khalil et al., Effect Of Acetylation And Coupling Agent Treatments Upon Biological Degradation Of Plant Fiber Reinforced Polyester Composites, Polymer Testing (2001) 20(1) 65-75; Prasad et al., Alkali Treatment Of Coir-Polyester Composites, J. of Materials Science (1983) 18(5), 1443-54; Rout et al., Novel Eco-Friendly Biodegradable Coir-Polyester Amide Biocomposites, Polymer Composites (2001) 22(6), 770-78; Rahman et al., Surface Treatment Of Coir Fibers And Its Influence On The Fibers Physico-Mechanical Properties, Composites Science and Tech. (2007) 67(11-12), 2369-76; Rozman et al., The Effect Of Lignin As A Compatibilizer On The Physical Properties Of Coconut Fiber-Polypropylene Composites, Eur. Polym. J. (2000) 36(7), 1483-94; Hai et al., Advanced Composite Materials, (2009) 18(3), 197-208; Tan et al., Advanced Materials Research (2010) 139-141, 348-51; Carvalho et al., BioResources (2010) 5(2), 1143-55; Silva et al., Composites Science and Technology (2006) 66(10), 1328-35; Javadi et al., Processing And Characterization Of Solid And Microcellular PHBV/Coir fiber Composites, Materials Science and Eng. (2010) 30(5) 749-57; Rosa et al., Bioresource Technology (2009) 100(21), 5196-5202; Geethamma et al., J. of Applied Polymer Science (1995) 55(4), 583-94; Geethamma et al., Polymer (1998) 39(6-7), 1483-91; Wei et al., Characterisation And Utilization Of Natural Coconut Fibres Composites, Materials and Design (2009) 30, 2741-44. Moreover, some studies have been reported on WG-based composites filled with natural fibers, such as, for example, hemp, jute, and coconut fiber (see, e.g., Kunanopparat et al., Plasticized Wheat Gluten Reinforcement With Natural Fibers: Effect Of Thermal Treatment On The Fiber/Matrix Adhesion, Composites: Part A (2008) 39, 777-85 and 1787-1792; Wretfors et al., Effects Of Fiber Blending And Diamines On Wheat Gluten Materials Reinforced With Hemp Fiber, J. of Materials Science (2010) 45(15), 4196-4205; Wretfors et al., J. of Polymers and the Environment (2009) 17(4), 259-66; Reddy et al., Biocomposites Developed Using Water-Plasticized Wheat Gluten As Matrix And Jute Fibers As Reinforcement, Polymer Int'l (2011) 60(4), 711-16; Muensri et al., Effect Of Lignin Removal On The Properties Of Coconut Coir Fiber/Wheat Gluten Biocomposite, Composites, Part A: Applied Science and Mfg. (2011) 42A(2), 173-79).
Some studies have been reported on the preparation of particleboard based on coconut materials. For example, high density particleboards from whole coconut husk have been produced without the addition of chemical binders (see, e.g., Van Dam et al., Ind. Crops Prod. 2004, 19(3), 207-216; Van Dam et al., Ind. Crops Prod. 2004, 20(1), 97-101; and Van Dam et al., Ind. Crops Prod. 2006, 24(2), 96-104). Moreover, CCP has been used for manufacturing particleboards using UF and PF as binders (see, e.g., Sampathrajan et al., Bioresour. Technol. 1992, 40(3), 249-251; Viswanathan et al., Bioresour. Technol. 1998, 67(1), 93-95; and Viswanathan et al., Bioresour. Technol. 2000, 71(1), 93-94). Additionally, insulating particleboards made from CCF with UF, PF and isocyanate binders have been reported (see, e.g., Khedari et al., Build. Envi. 2003, 38(3), 435-441). As noted above, there have also been some studies reporting on using modified WG as a binder for wood particleboards and fiberboards.
Thus, an interest exists for improved systems and methods for the production or fabrication of particleboard using non-formaldehyde-based binders. Stated another way, an interest exists for the design of improved formaldehyde-free particleboards. Moreover, a need remains for systems/designs for the fabrication of particleboards (e.g., formaldehyde-free particleboards) utilizing natural fibers/materials (e.g., lignocellulosic materials, such as coconut fibers and/or materials), wherein the particleboards have improved performance characteristics (e.g., mechanical properties) compared to conventional particleboards.
These and other inefficiencies and opportunities for improvement are addressed and/or overcome by the systems, assemblies and methods of the present disclosure.